"I think a lot of people really recognize that schools getting noes means it's time for our entire movement to step it up," said Rebecca Rast, 23, a senior at the University of California, Berkley. Rast attended a conference in Pittsburgh last month where hundreds of student activists shared information about the divestment campaign.

The Fossil Free campaign argues that it's wrong to put pollution into the air and contribute to climate change, so it's also wrong to profit from it. The strategy aims to limit the flow of capital to fossil fuel companies by making their stocks morally and financially unattractive. In theory, that could lead to a slowdown in how much fossil fuel is burned and more investments in renewable energy.

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Most schools haven't formally taken a position yet, but Fossil Free says about 15 have said no, including Boston College, Middlebury College and Vassar.

One expert on the history of social protest movements said the refusals may have been a strategic mistake, since there were other options, such as studying the issue further.

"It's kind of surprising," said Brian Obach, a professor of sociology at the State University of New York, New Paltz, and author of the book "Labor and the Environmental Movement."

"It's common for all movements to first ask decision makers for the change that they want, and to escalate tactics if they don't get what they're looking for," Obach said, adding that the schools that say no face another challenge. Climate change isn't going away, he said, so the divestment movement is likely to attract future students, too.

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At least eight schools have voted to divest: San Francisco State University; Foothill-De Anza Community College in Los Altos Hills, Calif.; Unity College and College of the Atlantic, both in Maine; Hampshire College in Massachusetts; and Sterling College and Green Mountain College, both in Vermont. Some cities, independent pension funds and religious groups also have started the process to divest.

Greta Neubauer, 22, a junior at Middlebury College in Vermont, said juniors and seniors in the Fossil Free movement already make a point of sharing tactics and lessons with freshmen and transfer students.

Rast, for instance, worked on the divestment campaign at Brown and is now active in California.

Middlebury students are now focusing on getting faculty and alumni mobilized, Neubauer said, and activists have created a new nationwide network to help students at different campuses share information and strategies.

At Brown University, a spokesman pointed to an Oct. 27 letter that President Christina H. Paxson wrote listing the reasons for not divesting from coal companies.

Paxson wrote that there is "no question" that human-caused environmental change "is among the most pressing issues of our time." But she argued that the parallels Fossil Free draws to tobacco companies and the anti-apartheid movement in South Africa don't exactly fit.

"Unlike tobacco, which arguably has no social value, a cessation of the production and use of coal would itself create significant economic and social harm to countless communities across the globe," Paxson wrote.

And unlike apartheid, the global economy is powered by coal, oil and natural gas. Renewable energy is growing and rapidly dropping in price, but experts say it will take many decades to completely replace fossil fuels. Reid Porter, a spokesman for the American Petroleum Institute, argued last May that oil and natural gas fuel the economy "in the most efficient and reliable way possible."

But when one tactic doesn't work, the Fossil Free movement tries another.

Drew O'Bryan, 21, a junior at the University of Illinois Urbana-Champaign, said that after trustees there declined requests for meetings, the movement organized an official student referendum last month, and about 86 percent voted for divestment. Last year, 72 percent of Harvard University's student body voted for divesting its $30 billion endowment.

"We're trying to go through the correct procedures and paths as we try and build power," O'Bryan said, and that means being determined, but respectful, so as not to "look like we're just extremists."

Neubauer said it was disappointing when Middlebury said no to divestment, since the school stresses environmental issues and sustainability. But it also was a wake-up call.

"I think for me it was sort of this moment of stepping back and recognizing that we need to" build a base to sustain the movement, he said.